Any feeling on putting a concrete slab on top of a red guard shower pan? I'm building a sauna in a shed and would like to use a liquid membrane redguard and rather than tile the final surface just leave it as concrete as I will put cedar strip boards on top of the floor surface. So it's not necessary to have a tiled surface. Could I pour a concrete slab in place of a second deck pan with tile on top.

Just spoke with Custom rep in California. He said that the concrete will not bond to the redgard and that will be a problem. SO....looks like i'm back to preslope, redgard membrane, mortar bed, tile. Just need to find some tile that I can live with at a reasonable price!

"Floor drain" doesn't tell me much. Is it a 3 pc clamping drain made for a shower? I'd put down a preslope then use the 3 pc clamping drain and Oatey pan liner instead of the Redgard. Then use deck mud like is usually done. Then tile on top of the mud. The mud bed won't bond to the liner, doesn't need to. If you can, post a pic of the drain.